Modular buildings typically comprise a skeletal metal (e.g., steel) frame that supports a number of elements allowing easy transportation, construction, and customization of the building unit. Those elements typically include a solid roof and floor and wall panels that are inserted into the frame. In order to provide access into the building unit, a door is typically provided on at least one of the walls of the building unit. However, installation of standard door assemblies into the modular assembly of a typical modular building unit has required that wall panels of the modular building unit be cut to receive a standard steel door frame. This often results in an unclean, unfinished appearance, a weak frame with low durability, and likewise often leaves gaps through which air will pass, making heating and cooling more difficult than if a properly sealed assembly were provided. An alternative is installation of a non-standard, custom door assembly that requires an expensive and complex aluminum design, requiring significant tooling investment and providing no flexibility.
Thus, there remains a need in the art for a modular building unit construction that allows fitment of a traditional door assembly, including a supporting door frame, that may be easily integrated with the modular wall panels of the modular building unit in a configuration that provides a more finished and clean appearance than previously known assemblies, and that provides a structurally reinforced frame, all while maintaining ease of transportability, installation, and customization of the modular building unit.